Re: [syzbot] [jfs?] UBSAN: array-index-out-of-bounds in dbSplit

[Edward Adam Davis]

check dmt_leafidx < 0 

#syz test: upstream 7846b618e0a4

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index cb3cda1390ad..c5b8883599e3 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -1956,6 +1956,7 @@ dbAllocDmapLev(struct bmap * bmp,
 {
 	s64 blkno;
 	int leafidx, rc;
+	dmtree_t *tp = (dmtree_t *) &dp->tree;
 
 	/* can't be more than a dmaps worth of blocks */
 	assert(l2nb <= L2BPERDMAP);
@@ -1964,10 +1965,10 @@ dbAllocDmapLev(struct bmap * bmp,
 	 * free space.  if sufficient free space is found, dbFindLeaf()
 	 * returns the index of the leaf at which free space was found.
 	 */
-	if (dbFindLeaf((dmtree_t *) &dp->tree, l2nb, &leafidx, false))
+	if (dbFindLeaf(tp, l2nb, &leafidx, false))
 		return -ENOSPC;
 
-	if (leafidx < 0)
+	if (leafidx < 0 || le32_to_cpu(tp->dmt_leafidx) < 0)
 		return -EIO;
 
 	/* determine the block number within the file system corresponding